Abstract:

Drainage continuity is very important for coalbed methane extraction. However, the well shut?in is unavoidable when draining. How to drain and draw up a reasonable drainage system after reopening the well are significant to increase gas production. Based on the analysis of coalbed methane production stage theory, combined with the field data about well shut?in, at the same time, numerical simulation method was used to study the change of reservoir parameters during well shut?in. The results show that well shut?in obviously changes the reservoir physical parameters,which causes the water saturation of the coal near the wellbore to increase, and the well bottom pressure increases. At the same time, it causes the re?adsorption of free gas near the wellbore and reduces the gas seepage capacity. Therefore, rapid drainage after reopening the well is helpful to dredge the flow channel of gas, improve gas flow capacity and increase gas production.

Key words: Coalbed methane, Well shut in, Drainage continuity, Rapid drainage, Rapid pressure drop

摘要：

排采连续性对煤层气开发至关重要。但是，在排采过程中关井现象不可避免，重新开井后如何排采、制定合理的排采制度是提高产量的关键。通过对煤层气生产阶段理论进行分析，结合关井前后矿场数据，同时借助数值模拟方法，对关井过程中储层参数变化进行了研究。结果表明，关井明显改变储层物性参数，造成井筒附近煤层含水饱和度增加，井底压力升高，同时引起近井地带自由气重新吸附，降低气体渗流能力。因此，重新开井后快速排水有助于沟通气体渗流通道，提高气体流动能力，增加产气量。

关键词: 煤层气, 关井, 排采连续性, 快速排采, 快速压降